Heat pipe

ABSTRACT

A heat pipe includes a hollow envelope, a wick bonded to an inner wall of the envelope, and a working fluid contained in a chamber inside the envelope. The wick is formed of sintering a plurality of first particles, which are made from copper, and a plurality of second particles, which are made from a material selected from the group consisting of silver, bismuth, indium, tin, and alloys thereof, together.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates a heat pipe and more particularly, to such a heat pipe, which is easy and inexpensive to manufacture.

2. Description of the Related Art

A regular heat pipe is generally comprised of a pipe body, a wick, and a working fluid. The pipe body is made from copper or copper alloy. The wick is sintered from copper powder and provided at the inside wall of the pipe body. Because the wick is a porous member having crevices, the working fluid can flow in the wick to achieve heat transfer by means of a capillary effect.

However, because the melting point of copper is as high as 1083° C., it is necessary to increase the temperature to about 900-1000 ° C. when sintering copper powder. This manufacturing process requires much working time, resulting in a high manufacturing cost.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a heat pipe, which is easy to fabricate, thereby effectively shorting the working time and reducing the manufacturing cost.

To achieve this object of the present invention, the heat pipe comprises a hollow envelope having an inside wall and a chamber, a wick containing a plurality of first particles and a plurality of second particles sintered together, and a working fluid contained in the chamber of the envelope. The wick is bonded to the inside wall of the envelope. The first particles are substantially made from copper and the second particles are made from a material selected from the group consisting of silver, bismuth, indium, tin, and alloys thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. I is a perspective view of a heat pipe according to the present invention.

FIG. 2 is a cross-sectional view taken in an enlarged scale along line 2-2 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a heat pipe 10 is shown comprised of a hollow envelope 20, an intermediate layer 30, a wick 40, a netting 50, and a working fluid 60.

The hollow envelope 20 has a tubular shape, and is made from copper or its alloy, for example copper-silver alloy. The envelope 20 defines a chamber 22 therein. The intermediate layer 30, the wick 40 and the netting 50 are provided in proper order at the inside wall of the envelope 20.

The intermediate layer 30 is formed of silver on the inside wall of the envelope 20 by electroplating. The intermediate layer 30 has a tubular shape. Alternatively, the intermediate layer 30 can be made from bismuth, indium, tin, or their alloy.

The wick 40 comprises a plurality of first particles 41 and a plurality of second particles 42. The first particles 41 and the second particles 42 are sintered together. The wick 40 has a tubular shape. The first particles 41 are substantially made from copper or its alloy. The second particles 42 are made from silver or its alloy. Actually, the second particles 42 can be made from silver, bismuth, indium, tin, or their alloy. The first particles 41 and the second particles 42 have particle size within about 0.01 μm to 15 μm.

The netting 50 is provided at the inner side of the wick 40. The netting 50 is made from copper-silver-phosphorus alloy in the shape of a tube. The mesh size of the netting 50 can be within about 100-325 meshes.

The working fluid 60 can be pure water or any of a variety of other solutions.

The working fluid 60 is received inside the envelope 20. By means of a capillary effect, the working fluid 60 is adhered to crevices in the wick 40 and the netting 50.

Because the melting point of silver is 960.5 ° C., it simply needs to increase the temperature to about 700-900 ° C. when sintering the mixture of the first particles 41 and the second particles 42. When sintered, the second particles 42 are bonded to the first particles 41. The second particles 42 act as a bonding agent. Further, silver content lowers the melting point of the netting 50, allowing quick bonding of the wick 40 and the netting 50 during sintering. Silver in the intermediate layer 30 acts as a bonding agent, for enabling the wick 40 to be bonded to the envelope 20 at a low temperature (700-900° C.).

In other words, the wick 40 contains a certain amount of the second particles 42 that lowers the working temperature of sintering. Silver in the intermediate layer 30 enables the wick 40 to be positively bonded to the envelope 20 below 900° C. The silver-contained netting 50 can also be positively bonded to the wick 40 below 900° C.

Therefore, the heat pipe according to the present invention can be made at a relatively lower working temperature. The fabrication procedure of the heat pipe according to the present invention is simple. Further, the invention saves much time in raising and lowering the temperature, thereby reducing the manufacturing cost. Further, the invention also saves much sintering time.

Further, the intermediate layer 30 is not imperative, and can be eliminated.

The wick 40, which contains the second particles 42, can be bonded to the envelope 20 by itself at a relatively lower temperature (700-900° C.). The netting 50 enhances the flowing and capillary action of the working fluid 60. However, the netting 50 can also be eliminated subject to different requirements.

Further, the melting point of bismuth is 271.3° C., the melting point of tin is 231.8° C., and the melting point of indium is 156.6° C. These melting points are all lower than copper's melting point 1083° C. Therefore, these materials can be used to replace the role of silver in the wick or the intermediate layer to lower the working temperature during sintering and to achieve the effects of the present invention. Further, phosphorus stabilizes the chemical properties of the netting. In addition, the netting 50 can be covered with a layer of coating material, which can be prepared from bismuth, indium, tin, or their alloy, for enabling the wick 40 and the netting 50 to be easily bonded together at a low temperature. 

1. A heat pipe comprising: a hollow envelope having an inside wall and a chamber; a wick containing a plurality of first particles and a plurality of second particles sintered together, said wick being provided at the inside wall of said envelope; wherein said first particles are substantially made from copper and said second particles are made from a material selected from the group consisting of silver, bismuth, indium, tin, and alloys thereof; and a working fluid contained in the chamber of said envelope.
 2. The heat pipe as claimed in claim 1, wherein said second particles have a particle size ranging from 0.01 μm to 15 μm.
 3. The heat pipe as claimed in claim 1, further comprising an intermediate layer arranged between the inside wall of said envelope and said wick, said intermediate layer being made from a material selected from the group consisting of silver, bismuth, indium, tin, and alloys thereof.
 4. The heat pipe as claimed in claim 1, wherein said wick has a tubular shape; the heat pipe further comprises a netting provided at an inner side of said wick.
 5. The heat pipe as claimed in claim 4, wherein said netting has a mesh size ranging from 100 meshes to 325 meshes.
 6. The heat pipe as claimed in claim 4, wherein said netting is made from copper-silver-phosphorus alloy.
 7. The heat pipe as claimed in claim 4, wherein said netting is coated with a layer of coating made from a material selected from the group consisting of bismuth, indium, tin, and alloys thereof.
 8. The heat pipe as claimed in claim 1, wherein said envelope is made from a material selected from the group consisting of copper and copper-silver alloy. 